The subject invention is directed generally to slant fringe reflection holograms, and more particularly to slant fringe reflection hologram structures that are substantially free of fringe breakout flare.
Slant fringe volume reflection holograms, wherein the hologram fringes are not parallel to the surfaces of the hologram, are being utilized in head-up displays for aircraft and automobile applications. An important consideration with slant fringe reflection holograms is fringe breakout flare which is a form of transmission hologram flare. Fringe breakout flare is the result of the fringes extending to and breaking the surfaces of the volume hologram to effectively form gratings at the surfaces which act as transmission holograms that are reconstructed by light from the outside such as sunlight at the appropriate angle. Fringe breakout flare is seen by the viewer as a series of rainbow-like patterns as one would see holding any transmission grating up to a light.
The problem of flare components in general has been addressed by procedures by reducing the reflections in the hologram construction system. However, since fringe breakout flare is inherent in slant fringe holograms wherein the fringes extend to and break the surfaces of the volume hologram, the cause of fringe breakout flare could not be removed by reducing construction system imperfections. A known technique directed specifically to reducing fringe breakout flare involves reducing the contrast of the fringes near the surfaces of the volume hologram. This technique produces holograms whose characteristics are difficult to predict and/or calculate, and may not be applicable to all holographic recording materials.